The short-short summary: build a two wheeled, self balancing car, similar in size and shape as a regular car, except with one wheel on each side, instead of two on each side.

Now, I know that someone's going to object that a segway-like vehicle must tilt forward to accellerate forward (or to slow
down, if it's moving backwards) and tilt backwards to accellerate backward (or to slow down, if it's moving forwards), resulting in the front or rear bumper scraping the road when high accelleration is needed, but... I have a solution.

Specifically, instead of moving the center of gravity forwards and backwards by tilting the car, move it some other way.

There are tree obvious ways of dynamically shifting the center of gravity without tilting the vehicle.

The first, is move a heavy mass forwards and backwards within the car, using the space where the driveshaft would normally go (if you use electric motors, one for each wheel, then you don't need a driveshaft). The problem of course is that this adds weight to the car that isn't really doing anything useful besides balancing, and it takes up quite a bit of space.

The second is to have a front and rear reservoir of some dense liquid, and pump this liquid forwards and backwards to move the vehicle's center of gravity. This has a variety of drawbacks (moving the liquid fast enough to balance the car, the added weight which isn't doing much useful, and leaks).

The third, and coolest idea, is to mount the two wheels (and perhaps their motors) on a pair of linear bearings (tracks or rails or rolamite), and move the entire vehicle forwards and backwards on them.

One important side effect of moving the center of gravity without in this manner is that we no longer need to turn the wheels to balance; the car can balance itself even if it's in park or neutral, or with the emergency brake on, or (and perhaps most importantly) even if it's skidding around on an icy surface.

Another advantage is that the computer circuitry for balancing can be made independant of the rest of the car's computer circuitry, making it more robust and crash resistant (no pun intended). In a segway, balancing and accelleration are and must be integrated.-- goldbb,
Jan 06 2009

Fun visuals, imagining your idea.
What would happen when two bumped into one
another while heading towards each other (head-
on fender bender for example)? I imagine an
acceleration response initially. Also thnx for
introducing Rolamite to me.-- Sir_Misspeller,
Jan 06 2009

What would be wrong with allowing the two
wheeler only slide the mass to stay balanced.

Now imagine removing the wheels, and, on each side of the car, extending the front and rear wheel wells towards each other and joining them, making one extra long wheel well on each side of the car.

Now put a track or rail extending from the front to the back of each of these two long wheel wells.

Mount one electric motor and wheel onto each track (that's one wheel on the left side of the car, and one on the right).

Attach to each electric motor, two hydraulic cylinders: one cylinder attaches the motor to the front of the wheel well and the other to the rear of the wheel well, to push/slide the motor (and it's attached tire, of course) towards the front or rear of the vehicle.-- goldbb,
Jan 07 2009

I think we need some figures for maximum acceleration (and deceleration if you're thinking about emergencies). Something involving newton-metres and miles per hour.-- bigsleep,
Jan 07 2009

//Something involving newton-metres and miles per hour//

Don't you mean newton.metres and kilometers per hour? Or even better, metres per second? I mean we can stick with the old fathoms-per-fourlong stye measurements if you like, but do try not to taint our lovely metrics with your slovenly imperials.

I personally think you'd end up with a relationship between newton metres and metres per second squared. Velocity wouldn't matter a damn, it's the acceleration that you need to counter with an offset mass.-- Custardguts,
Jan 08 2009

Why not just use a large gryo, and sense the force on it? Self levelling without the electronics.

You say , 'our', asifit has any reason for a sense of
personal pride. Ha! Last time I checked your 'ours'
was everyone except the USA and some tiny
backwards place that used beads to tell
temperature. Just the two of us, The USA and
that other weird place use anything but metrics.
So, ha ha. :)) \\ but do try not to taint our
lovely metrics with your slovenly imperials
\\-- Sir_Misspeller,
Jan 08 2009

Sir_Misspeller, why would there necessarily be balancing involved if a segcar ran into another vehicle (or a wall)?

There's no reason to expect there to be any collision-induced torque pushing either car upwards or downwards, at least if their bumpers are at the same height (which would surely be the case if they were both segcars.)

bigsleep, the max accelleration or decelleration (linear, not rotational) will depend purely on the strength of the electric motors spinning the wheels, and the braking ability at the wheels. (And the number of amps the battery can supply to the motor, and the traction on the road, etc.)

Of course, if you're asking what are the maximum plus and minus accellerations that the car can balance at, that's a little more complicated.

When the car is accellerating forwards, the total accelleration force vector on the car can be decomposed into two parts: the upwards force of the road on the car (in response to the gravity induced downwards force of the car towards the road), and the forwards force of the road on the wheels. If these two parts, when are added together and projected from the point of contact between wheel and road, point straight towards the car's center of gravity, then there will be no net torque on the car (meaning that the car can be balanced).

This means that if the car is accellerating forwards (or backwards) at a rate of 1 g, then a triangle down from the c.o.g. of the car to the ground, back to the wheels, and back to the c.o.g., would be a right isocolese triangle, in order to keep balanced.

Basically, the distance (measured from "center") towards the rear that the motor/wheel assemblies need to be is equal to the distance from the c.o.g. to the ground multiplied by the number of gs of forward accelleration.

Of course, this only describes how long the track / linear bearing needs to be.

The amount of force needed to hold the motors in place, whether newtons or pounds, is going to be exactly equal to the amount of accelleration being applied between the road and wheel.

As for a relation between newton-meters and miles per hour... Actual speed is irellevent, only accelleration is relevant.-- goldbb,
Jan 08 2009

The water bags, at Luke warm (body)
temperature, inside the vehical ,would not slow
as fast as the two wheeler.Not as fast as the
machine, in a head-on.
So, it then,
seemed to my imagination that, mass going
forwards inside, in relation to the machines
centering, caused a forward response.-- Sir_Misspeller,
Jan 08 2009

now who is Luke and how did he get a temperature range named after him ?-- FlyingToaster,
Jan 08 2009

as you may already of guessed, my spelling is
telling. I used the spell-checker and it not I am
responsible.